Now, the service has been re-created as a third-rate Yelp instead of a first-rate Foursquare. Check-ins are now done via Swarm, a new app launched recently by Foursquare.

The trouble with this is that, for many of Foursquare's most loyal and passionate users, checking in to locations is what Foursquare has always been about.

This kind of late-stage pivoting is something of an unhappy trend. I believe the cause of these strategic errors by companies is a combination of taking longtime and passionate users for granted while simultaneously coveting thy neighbor's business model.

That's a risky strategy. A company that goes that route could fail to succeed with the new model and also fail to hang on to its most passionate users. Then it could be acquired by Yahoo, never to be heard from again.

People who love Twitter fell in love with it when it was a hyper-minimalist, quirky, secret-code-controlled text-centric microblog. It was minimalism that made Twitter great.

But Twitter got a bad case of Google and Facebook envy. The company redesigned its spare minimalism to look almost exactly like cluttered Facebook. The CEO of a company called Berg illustrated this perfectly by putting his Twitter and Facebook profiles side by side. The redesign is part of a larger direction for Twitter streams to move from text-based to picture-based. Twitter is joining Google+ and Facebook in the arms race that has broken out as people use images, rather than words, to compete for attention.

Twitter also embraced the card interface, which Google has rolled out to multiple properties, from Google+ to Android Wear.

Twitter has recently been testing a feature called " retweet with comment," which gathers up the original tweet in a card and essentially attaches it to the retweet. This moves Twitter away from its core idea, which is forced brevity.

Of course, new features can fail their tests and may never be rolled out. But the nature of Twitter tests suggests that the company is making the dual mistakes of taking its core user base for granted and simultaneously flirting with the business models of competitors.

Twitter is even considering dropping both the @ symbol, for identifying and linking to specific user accounts, and the hashtag, for linking to specific kinds of content, according to some testing it has done.